An artificial synapse based on oxygen-ion-driven electrochemical random-access memory (O-ECRAM) devices is a promising candidate for building neural networks embodied in neuromorphic hardware. However, achieving commercial-level learning accuracy in O-ECRAM synapses, analog conductance tuning at fast speed, and multibit storage capacity is challenging because of the lack of Joule heating, which restricts O2- ionic transport. Here, we propose the use of an atomically thin heater of monolayer graphene as a low-power heating source for O-ECRAM to increase thermally activated O2- migration within channel-electrolyte layers. Heating from graphene manipulates the electrolyte activation energy to establish and maintain discrete analog states in the O-ECRAM channel. Benefiting from the integrated graphene heater, the O-ECRAM features long retention (>104 s), good stability (switching accuracy <98% for >103 training pulses), multilevel analog states for 6-bit analog weight storage with near-ideal linear switching, and 95% pattern-identification accuracy. The findings demonstrate the usefulness of 2D materials as integrated heating elements in artificial synapse chips to accelerate neuromorphic computation.
Keywords: 2D materials; ECRAM; artificial neural network; electronic synapse; graphene heater; neuromorphic computing; training accelerator.